You were only eligible to receive credit if you had a U.S. billing address and purchased a Kindle book between April 1, 2010, and May 21, 2012, published by one of five major U.S. publishers: Hachette, HarperCollins, Macmillan, Penguin and Simon & Schuster.

The case, which was settled Nov. 21, 2014, addressed the question of whether Apple and the five listed publishers conspired to fix and raise the retail prices of eBooks.

“Under the settlements, Apple provided funds for credits that were applied directly to Amazon accounts of eligible customers in June 2016,” Amazon explains. “These credits expired in June 2017. Customers who redeemed credits from the June 2016 distribution received additional credits in October 2017.”

Amazon was not on either side of the lawsuit but, as a major retailer that maintains an 80 percent share of the electronic book market, has opted to distribute credit to Kindle-reading customers directly.

Some retailers, like Google, are requiring customers to file Claim Forms to participate in the settlement. But most, including Barnes & Noble, are sending out emails like Amazon to notify customers about available credit.

If you have received credit, it will be automatically applied to your next Amazon purchase, and “will appear as a gift card in your order summary during checkout,” the site says.

So check your emails from Wednesday, and, if you see a credit, be sure to use it before it expires on April 20, 2018.